Ligand exchange processes of OsHCl(CO)(L)(PR3)2 (L=vacant, H2, R′CN, O2; R=Cy, i-Pr)
作者:J.Scott Parent、Neil T. McManus、Garry L. Rempel、William P. Power、Todd B. Marder
DOI:10.1016/s1381-1169(98)00005-3
日期:1998.10
The reactivity of complexes formed by the addition of O-2, H-2 and R'CN to OsHCl(CO)(PR3)(2) (1a:R = Cy; 1b:R = i-Pr) has been examined. Under 24 bar H-2 and 65 degrees C, the dioxygen ligand of OsHCl(CO)(O-2)(PR3)(2) (2a,b) is displaced to yield the trans-hydridodihydrogen complexes OsHCl(eta(2)-H-2)(CO)(PR3)(2) (3a,b). Measurements of the equilibrium constant, K-H2 = [3a]/[1a][H-2], for the direct addition of H-2 to 1a yield Delta H degrees = -49.1 +/- 2.4 kJ/mol and Delta S degrees = -95.7 +/- 7.9 J/mol K. 1a,b react reversibly with aryl and alkyl nitriles to produce the isolable complexes, OsHCl(CO)(R'CN)(PR3)(2) (4a,b). The phosphine ligands of la,b and 3a,b exchange with unbound, bulky alkyl phosphines at a rate that is slow relative to the NMR timescale. In the presence of excess PCy3, complex 3b yields the exchange products OsHCl(eta(2)-H-2)(CO)(Pi-Pr-3)(PCy3) and 3a. While a tris-phosphine complex cannot be detected, limited kinetic data characterize the exchange as associative process. (C) 1998 Elsevier Science B.V. All rights reserved.